It’s very quick and easy in Chiang Mai. Walk past the security gate, then turn left and you will see a waiting area outside. There will be a stack of forms and one of them is the 90 day report form TM 47. Fill that out, and bring it to the 90 day report section window. It’s also outside and there is a drive thru. Simply present your passport and TM47. You don’t need anything else. You’ll probably be at immigration no more than 30 minutes. Good luck!